CAS number 1303-96-4 (decahydrate) YesY
ChemSpider 17339255 YesY
EC number 215-540-4
Jmol-3D images Image 1
Molecular formula Na2B4O7·10H2O or Na2[B4O5(OH)4]·8H2O
Molar mass 381.37 (decahydrate)
Appearance white solid
Density 1.73 g/cm³ (solid)
Melting point

743 °C (anhydrous) [1]

Boiling point

1575 °C

Related compounds
Other anions Sodium aluminate; sodium gallate
Other cations Potassium tetraborate
Related compounds Boric acid, sodium perborate
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
Old steam tractor and Borax wagons, Death Valley

Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. It is usually a white powder consisting of soft colorless crystals that dissolve easily in water.

Borax has a wide variety of uses. It is a component of many detergents, cosmetics, and enamel glazes. It is also used to make buffer solutions in biochemistry, as a fire retardant, as an anti-fungal compound for fiberglass, as an insecticide, as a flux in metallurgy, a texturing agent in cooking, and as a precursor for other boron compounds.

The term borax is used for a number of closely related minerals or chemical compounds that differ in their crystal water content, but usually refers to the decahydrate. Commercially sold borax is usually partially dehydrated.

The word borax is Persian and originates in the Middle-Persian būrak.

Borax first came into common use in the late 19th century when Francis Marion Smith's Pacific Coast Borax Company began to market and popularize a large variety of applications under the famous 20 Mule Team Borax trademark, named for the method by which borax was originally hauled out of the California and Nevada deserts in large enough quantities to make it cheap and commonly available.[2][3]



Borax-based washing detergent.

Household products

Borax is used in various household laundry and cleaning products,[4] including the "20 Mule Team Borax" laundry booster and "Boraxo" powdered hand soap. However, despite its name, "Borateem" laundry bleach no longer contains borax or other boron compounds.

Borax is also present in some tooth bleaching formulas.[5]


Sodium borate is used in biochemical and chemical laboratories to make buffers, e.g. for gel electrophoresis of DNA, such as TBE or the newer SB buffer or BBS (borate buffered saline) in coating procedures. Borate buffers (usually at pH 8) are also used as preferential equilibration solution in DMP-based crosslinking reactions.


Borax as a source of borate has been used to take advantage of the co-complexing ability of borate with other agents in water to form complex ions with various substances. Borate and a suitable polymer bed are used to chromatograph non-glycosylated hemoglobin differentially from glycosylated hemoglobin (chiefly HbA1c), which is an indicator of long term hyperglycemia in diabetes mellitus. Borate and a proprietary synthetic amino acid, Deselex (from Henkel) have been used to complex water "hardness" cations to make a non-precipitating water "softener". Borate alone does not have a high affinity for "hardness" cations, although it has been used for that purpose.


A mixture of borax and ammonium chloride is used as a flux when welding iron and steel. It lowers the melting point of the unwanted iron oxide (scale), allowing it to run off. Borax is also used mixed with water as a flux when soldering jewelry metals such as gold or silver. It allows the molten solder to flow evenly over the joint in question. Borax is also a good flux for 'pre-tinning' tungsten with zinc - making the tungsten soft-solderable.[6]

Small-scale mining

Borax is replacing mercury as the preferred method for extracting gold in small-scale mining facilities. The method is called the borax method and is used in the Philippines.[7]


A rubbery polymer sometimes called flubber, gluep or glurch can be made by cross linking polyvinyl alcohol with a borax. Making flubber from polyvinyl acetate based glues, such as Elmer's Glue, and borax is a common elementary education experiment.[8]

Food additive

Borax, given the E number E285, is used as a food additive in some countries but is banned in the United States. As a consequence, certain foods, such as caviar, produced for sale in the U.S. contain higher levels of salt to assist preservation.[9] Its use as a cooking ingredient is to add a firm rubbery texture to the food, or as a preservative. In oriental cooking it is mostly used for its texturing properties. In Asia, Borax (Chinese: 硼砂; pinyin: péng​ shā​) or (Chinese: 月石; pinyin: yuè shí​) was found to have been added to some Chinese foods like the hand-pulled noodles lamian and some rice noodles like Shahe fen, Kway Teow, and Chee Cheong Fun recipes.[10] In Indonesia it is a common, but forbidden, additive to such foods as noodles, bakso (meatballs), and steamed rice. The country's Directorate of Consumer Protection warns of the risk of liver cancer with high consumption over a period of 5–10 years.[11]

Other uses

Natural sources

Borax "cottonball"

Borax occurs naturally in evaporite deposits produced by the repeated evaporation of seasonal lakes. The most commercially important deposits are found in Turkey; Boron, California; and Searles Lake, California. Also, it has been found at many other locations in the Southwestern United States, the Atacama desert in Chile, and in Tibet and Romania. Borax can also be produced synthetically from other boron compounds. Naturally occurring Borax, (known by the trade name Rasorite - 46 in USA and many other countries) is refined by a process of re-crystallization.[17]


Borax, sodium tetraborate decahydrate, is not acutely toxic.[18] Its LD50 (median lethal dose) score is tested at 2.66 g/kg in rats:[19] a significant dose of the chemical is needed to cause severe symptoms or death. The lethal dose is not necessarily the same for humans.

Sufficient exposure to borax dust can cause respiratory and skin irritation. Ingestion may cause gastrointestinal distress including nausea, persistent vomiting, abdominal pain, and diarrhea. Effects on the vascular system and brain include headaches and lethargy, but are less frequent. "In severe poisonings, a beefy red skin rash affecting palms, soles, buttocks and scrotum has been described. With severe poisoning, erythematous and exfoliative rash, unconsciousness, respiratory depression, and renal failure." [20]

A reassessment of boric acid/borax by the United States Environmental Protection Agency Office of Pesticide Programs found potential developmental toxicity (especially effects on the testes).[21] Boric acid solutions used as an eye wash or on abraded skin are known to be particularly toxic to infants, especially after repeated use, because of the slow elimination rate.[22]

Borax was added to the Substance of Very High Concern (SVHC) candidate list on 16 December 2010. The SVHC candidlate list is part of the EU Regulations on the Registration, Evaluation, Authorisation and Restriction of Chemicals 2006 (REACH), and the addition was based on the revised classification of Borax as toxic for reproduction category 1B under the CLP Regulations. Substances and mixtures imported into the EU which contain Borax are now required to be labelled with the warnings "May damage fertility" and "May damage the unborn child".[23]


The structure of the anion [B4O5(OH)4]2− in borax

The term borax is often used for a number of closely related minerals or chemical compounds that differ in their crystal water content:

  • Anhydrous borax (Na2B4O7)
  • Borax pentahydrate (Na2B4O7·5H2O)
  • Borax decahydrate (Na2B4O7·10H2O)

Borax is generally described as Na2B4O7·10H2O. However, it is better formulated as Na2[B4O5(OH)4]·8H2O, since borax contains the [B4O5(OH)4]2− ion. In this structure, there are two four-coordinate boron atoms (two BO4 tetrahedra) and two three-coordinate boron atoms (two BO3 triangles).

Borax is also easily converted to boric acid and other borates, which have many applications. Its reaction with hydrochloric acid to form boric acid is:

Na2B4O7·10H2O + 2 HCl → 4 B(OH)3 [or H3BO3] + 2 NaCl + 5 H2O

The "decahydrate" is sufficiently stable to find use as a primary standard for acid base titrimetry.[24]

When borax is added to a flame, it produces a yellow green color.[25] This property has been tried in amateur fireworks,[citation needed] but borax in this use is not popular because its waters of hydration inhibit combustion of compositions and make it an inferior source of the boron that is responsible for most of the green color, and that is overwhelmed by the yellow contributed to the flame by sodium.

However, commercially available borax can be mixed with flammables such as methanol to give the characteristic green flame of boron when ignited, which then slowly gives way to the characteristic yellow-orange flame of the sodium.

See also


  1. ^ CRC Handbook of Chemistry and Physics 86th edition (2005-2006) section 4 page 88
  2. ^ "American Borax Production" Scientific American September 22, 1877
  3. ^ Hildebrand, G. H. (1982) "Borax Pioneer: Francis Marion Smith." San Diego: Howell-North Books. p. 267 ISBN 0-8310-7148-6
  4. ^ Record in the Household Products Database of NLM
  5. ^ Hammond, C. R. (2004). The Elements, in Handbook of Chemistry and Physics 81st edition. CRC press. ISBN 0849304857. 
  6. ^ Dodd, J.G. (1966). "Soft soldering to tungsten wire". Am. J. Phys 34 (10): xvi. doi:10.1119/1.1972398 
  7. ^ "The borax method". Borax replacing mercury in small-scale mining. The Geological Survey of Denmark and Greenland (GEUS). Retrieved 2008-08-02. 
  8. ^ Parratore, Phil. Wacky Science: A Cookbook for Elementary Teachers. Dubuque, IA: Kendall Hunt. p. 26. ISBN 0787227412. 
  9. ^ "Caviar glossary". The Caviar Guide a gourmet review of caviars & fish roe. Hanson Ltd, Geneva, Switzerland. Retrieved 2008-07-07. 
  10. ^ Chinese Ingredients: Borax Powder, Sep 11, 2005, Chow Hound, Home Cooking
  11. ^ Staff writer (2006). "Watch Out For The Food We Consume". Directorate of Consumer Protection, Jakarta, Indonesia. Retrieved 2009-02-10. 
  12. ^ Centre for Alternative Technology 2006 sheep wool insulation publication
  13. ^ Borax at UC Berkeley
  14. ^
  15. ^ Radweld safety data sheet Retrieved 19-02-2010
  16. ^ Step-By-Step Slime Instructions
  17. ^ Wizniak, Jaime (July 2005). "Borax, Boric Acid, and Boron—From exotic to commodity". Indian Journal of Chemical Technology (New Delhi: Council of Scientific and Industrial Research) 12 (4). ISSN 0975-0991. 
  18. ^ Borax - toxicity, ecological toxicity and regulatory information
  19. ^ Mountain Fresh Dial Bar Soap
  20. ^ Borax - toxicity, ecological toxicity and regulatory information
  21. ^ Report of the Food Quality Protection Act (FQPA) Tolerance Reassessment Eligibility Decision (TRED) for Boric Acid/Sodium Borate Salts
  22. ^ Goodman and Gillman's: The Pharmacological Basis of Therapeutics, 6th edition, chapter on Antiseptics and Disinfectants, page 971
  23. ^
  24. ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M.J.K.; Denney, R. C.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York: Prentice Hall, ISBN 0-582-22628-7  p 316.
  25. ^ Staff. "Creating Flame Colors". The Science Company. Retrieved November 30, 2008. 

External links

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Look at other dictionaries:

  • borax — borax …   Dictionnaire des rimes

  • Borax — Kristalle aus Kalifornien Chemische Formel Na2[B4O5(OH)4] · 8 H2O …   Deutsch Wikipedia

  • Borax — Cristaux de borax Général Nom IUPAC …   Wikipédia en Français

  • Borax — (Natriumborat, Natriumtetraborat, borsaures Natrium) Na2B4O7, kristallisiert in der Regel mit 10 H2O als prismatischer Borax, kann aber auch mit 5 Molekülen Wasser als oktaedrischer Borax erhalten werden. Im kristallisierten Zustande bildet er… …   Lexikon der gesamten Technik

  • borax — [ bɔraks ] n. m. • 1611; borrache 1256; lat. médiév. borax; ar. buraq « salpêtre », du persan burah ♦ Sel cristallin blanc (Na2B4O7), à saveur alcaline, utilisé pour la soudure des métaux et dans la fabrication du verre, des émaux, des savons et… …   Encyclopédie Universelle

  • BORAX-I — Saltar a navegación, búsqueda Los Experimentos BORAX, experimentos del reactor de agua en ebullición, fueron una serie de pruebas en la utilización del reactor nuclear BORAX I que demostraron la teoría de 1952 de Samuel Untermyer de que un… …   Wikipedia Español

  • borax — BÓRAX, s.n. Borat de sodiu. – Din fr. borax. Trimis de valeriu, 13.09.2007. Sursa: DEX 98  BÓRAX s. (chim.) tetraborat de sodiu. Trimis de siveco, 05.08.2004. Sursa: Sinonime  bórax s. n. Trimis de siveco, 10.08.2004. Sursa: Dicţionar… …   Dicționar Român

  • Borax — Sm borsaures Natrium per. Wortschatz fach. (16. Jh.), fnhd. borros, buras Entlehnung. Entlehnt als borros u.ä. aus ml. borax f./n. Dieses geht über arab. būraq, bauraq auf pers. būräh zurück. Später wird erneut auf die mittellateinische Form… …   Etymologisches Wörterbuch der deutschen sprache

  • Borax — Bo rax, n. [OE. boras, fr. F. borax, earlier spelt borras; cf. LL. borax, Sp. borraj; all fr. Ar. b?rag, fr. Pers. b?rah.] A white or gray crystalline salt, with a slight alkaline taste, used as a flux, in soldering metals, making enamels, fixing …   The Collaborative International Dictionary of English

  • borax — [bôr′aks΄] n. [ME < ML borax < Ar bauraq < Pers būrah] 1. sodium borate, a white, anhydrous, crystalline salt, Na2B4O7, with an alkaline taste, used as a flux in soldering metals and in the manufacture of glass, enamel, artificial gems,… …   English World dictionary

  • Borax — (Natriumborat, Natriumtetraborat, borsaures Natron) Na2B4O7+10H2O findet sich an der Grenze der Natronsalpeterfelder in Peru und Bolivia, gelöst in Seen Chinas, Tibets (Teschu Lumbu), der südlichen Tatarei, Nepals, Persiens, Ceylons, in… …   Meyers Großes Konversations-Lexikon

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